<?php
	function distance($lat1, $lon1, $lat2, $lon2) { 

		$theta = $lon1 - $lon2; 
		$dist = sin(deg2rad($lat1)) * sin(deg2rad($lat2)) +  cos(deg2rad($lat1)) * cos(deg2rad($lat2)) * cos(deg2rad($theta)); 
		$dist = acos($dist); 
		$dist = rad2deg($dist); 
		$miles = $dist * 60 * 1.1515;
		$unit = strtoupper($unit);

		return $miles * 1609.344;
	}
?>